Production of tertiary olefins



D. R. STEVENS ET AL PRODUCTION OF TERTIARY OLEFINS Dec. 9,1941.

Filed June 26, 1940 Dona Id R. swans f]. 6 rue e/ Patented Dec. 9, 1941 UNITED STATES PATENT OFFICE PRODUCTION OF TERTIARY OLEFINS Donald R. Stevens, Swissvale, and William A.

Gruse, Wilkinsburg, Pa., assignors to Gulf Research a Development Company, Pittsburgh, Pa., a corporation of Pennsylvania Application June 26, 1940, Serial No. 342,584

7 Claims.

thereby selectively removing the tertiary olefin from the mixture, the charged extracting fluid is separated from the residual hydrocarbon vapors and is heated to a temperature of 100 to 300 C. to release the tertiary olefin, the tertiary olefin is recovered and the extracting fluid is cooled and contacted with further quantities of the hydrocarbon mixture containing the tertiary olefin; all as more fully hereinafter described and as claimed. 1

Olefins such as isobutylene, trimethylethylen and the like which hydrate to form tertiary alcohols are quite reactive and commercially very useful. Thus, they can be used to alkylate phenols, forming tertiary alkyl phenols which are useful as antioxidants and as insecticides and germicides; or for alkylating isoparafiins, such as isobutane, to produce high octane gasoline. High octane gasoline can also be produced by polymerizing certain of the above described olefins, notably isobutylene, by means of heat in the presence of sulfuric acid or some other suitable agent. High molecular weight resins are also prepared by polymerizing such olefins. The present invention is concerned with the recovery of such olefins in substantially pure form and they are referred to herein and in the appended claims as tertiary" olefins.

In the cracking of petroleum oils considerable amounts of tertiary olefins are produced in admixture with other hydrocarbons such as the parafllns and normal and secondary olefins. For example in the production of ordinary grades of gasoline it is frequent practice to remove by distillation from th condensate made in pressure cracking a highly volatile fraction which consists essentially of a mixture of four carbon hydrocarbons, butane and the butylenes, including isobutylene. This fraction is known as the butane cut or C4 cut and is an extremely volatile liquid, boiling at 10 to 6 C. at atmospheric pressure. A similar fraction known 'as the pentane or C out which is composed of a mixture of pentane and the amylenes including tri-methyl-ethylene may also be obtained. Similar liquids are also obtainable by debutanizing or "depentanizing the gas from cracking operations which oftencontain liqueiiable vapors.

While these petroleum cracking products com posed of mixtures of hydrocarbons of the same number of carbon atoms are readily obtainable it has been found diflicult to isolate the tertiary olefins from these mixtures. One method which has been proposed for this purpose is to selectively absorb isobutylene from a C4 cut by means of to per cent sulfuric acid solution. This method is highly selective but is difficult to operate economically because of the polymerizing action of sulfuric acid on isobutylene.

It is an object achieved by the present invention to provide a process for the isolation of substantially pure tertiary olefins from their mixtures with other hydrocarbons of the same numwith an extracting fluid composed essentially of a mixture of phenols and an acid condensing agent, at a temperature of 20 to C., separating the charged extracting fluid from the residual petroleum products, heating the charged extracting fluid to a temperature of to 300 C., collecting the tertiary olefin gas thus liberated, cooling the extracting fluid to a temperature of 20 to 80 C., and contacting it with further quantities of the hydrocarbon mixture containing the tertiaryolefin. By repeating this series of steps in a cyclic method we have been able to produce substantial quantities of tertiary olefins continuously and without excessive losses due to polymerization or side reactions.

In carrying out the method of our invention,

the extracting fluid is advantageously made up from mixtures of phenols, such as phenol itself and its lower homologues such as the cresols, xylenols or ethyl phenols which are not substantially decomposed by heating to a temperature of 100 to 300 C. in the presenc of an acid co'ndensing agent. Mixtures of phenols such as the commercially available cresol mixtures and cresylic acids have proved particularly satisfactory. Substantially pure phenols, such as phenol or pcresol may also be used, but the products tend to solidify and they are less desirable for the purposes of this invention.

A wide variety of acid condensing agents may 2 be incorporated in the phenol to produce the extracting fluid. For example sulfuric acid,

either alone or admixed with a mitigating agent such as a polyhydric alcohol or an alkali metal; sulfate may be used, or a sulfonic acid or an- 1 hydrous aluminum chloride or a molecular compound of aluminum chloride. The exact amount of acid condensing agent used will vary with the eii'ectiveness of the particular agent and may be regulated to control the rate at which the tertiary olefin can be taken up by the extracting fluid and to control any tendency there may be to-;

ward polymerization or side reactions at the temperature being used.

corresponding to about 0.01 to 3.0 per cent by weight of the phenolic material produce satis-.

factory results. Within this range when sulfuric acid is used alone it is generally advantageous to use amounts in the lower part of .the range in order to avoid the tendency of sulfuric acid to cause polymerization of the tertiary ole'flns.

If. however, a mitigating agent is used, larger amounts of sulfuric acid within this range may be used without substantial polymerization. The

sulfonic acids exhibit little tendency toward poly- 1 merization or side reactions, and are highly efllcient and it is generally unnecessary to use more 1 than about 2.0 per cent for satisfactory results. Anhydrous aluminum chloride also tends to produce polymerization and side reactions and is 1 In general amounts 1 advantageously used in the minimum eifective amount, but the molecular compounds of aluminum chloride show less of this tendency and larger amounts of these compounds may be used advantageously to obtain'high extraction rates; 1 After a suitable mixture of phenols and acid condensing agent has been prepared this extract ing fluid is contacted with the hydrocarbon mixture from which the tertiary olefin is to be reing fluid for example by bubbling the vapor through the liquid or by countercurrent flow in a contact tower.

' covered. 'I'hiscontacting maybe carried out by various means. In most cases we have found it advantageous to contact the hydrocarbon mixture in the vapor phase with the liquid extract The temperature during this 1 contact should be maintained below about 80 C.,

advantageously about to 70 C. The time of contact may be regulated by the rate of flow of the vapor and should be such that the residual vapors passing out of contact with the extracting fluid are substantially free from tertiary olefin.

The charged extracting fluid after separation I i from the residual vapors is heated to a tem-' perature of about 100 to 300 0. to liberate the 1 contained iso-olefin. This operation is advan- After separation and recovery of the iso-olefln,

1 the extracting fluid is cooled to a temperature of 20 to 80 C. and is contacted with further quantities of the hydrocarbon mixture containing the 3 3 iso-olefln and the series of steps above outlined is repeated. By this cyclic operation a con- 1 tinuous supply of 'iso-oiefln' may be obtained. 1 The amount of polymerization and side reaction or decomposition which takes place in'each cycle is so small that the same extracting fluid may be used for relatively long periods before contamination makes its further use uneconomical.

In the accompanying drawing there is illustrated diagrammatically one form of apparatus suitable for carrying out the method of our invention in the continuous production of substanpacked or suitably baflied tower, provided with a temperature control means ll, such as heating or cooling jackets. Chamber I. is provided at its bottom with an inlet. l2 through which the hydrocarbon mixture from vaporizer 9 may be introduced, and at its top with an outlet containing back-pressure valve l3 through which the residual vapors may be exhausted. Holding tanks 33 and 34 are connected through pumps 35 and 36 respectively and conduit II with the top of chamber I0. Chamber I0 is connected at its bottom through conduit l5, pump it and preheater H with the main heating chamber It provided with heating coil l9. Heating chamber I8 is provided at its top with a packed tower section 20 and an outlet 2! through which the released iso-olefin is carried oiI. Outlet 2| is connected with a cooling coil 22 andaccumulator 23 in which any phenol condensed out of the isoolefin vapors is collected and returned to tower 20 through conduit 24. Accumulator 23 is connected through conduit 25 with an alkali scrubber 26 which in turn is connected through conduit 21, compressor 28 and conduit 29. with condenser 30 and a suitable iso-olefin collecting system (not shown).

The main heating chamber I8 is connected at its bottom through conduit 4| with a cooling coil 42 which in turn is connected through conduit 43 with asettling drum 44. The settling drum 44 is connected through conduit 45, pump 49 and conduit 41 with conduit I4 and the top of the contact chamber l0. An outlet 48 is provided at the bottom of settling chamber 44 through which ex-' tracting fluid may-be bled ofl as desired for reconditioning.

The method of my invention may be carried out in this apparatus for example in the recovery of isobutylene from a C4 cut using a mixture of commercial cresol containing 2.0 per cent of disec-butyl sulfate as the extracting fluid, as 1'01- lows:

Cresol and di-sec-butylsulfate in proper portion are introduced from holding tanks 33 and 34 through pumps 35 and 36 respectively and conduit l4 into the top of chamber l0 where it flows down over the packing material or baflies as the case may be. The C4 cut is vaporized in vaporizer 9 and is introduced into the bottom of chamber i0 through conduit I2 and passes upward through the packing or baiiles where it contacts the downcoming extraction fluid. A suitable rate of flow is established so that the contact time between the liquid and vapor is such that all or most of the isobutylene in the vapors is extracted by the liquid, and the temperature is maintained below about 70 C. by introducing cooling fluid into jackets ll. The residual vapors are exhausted through back pressure valve l3.

The charged extracting fluid is pumped 01!.

through conduit l5 by pump l6 and is introduced into the preheater H, where it is brought at least part of the way to dealkylation temperature, and

r passes into the main heating chamber l8 which has previously been brought to a suitable temperature, usually about 200 C. by means of heating coil IS. The charged fluid may be thoroughly agitated in this chamber to facilitate rapid separation of the isobutylene.

The liberated isobutylene rises through tower 20 where entrained phenols are separated from the vapors and returned to chamber I8. The isobutylene vapor is carried out of tower 20 through conduit 2| to cooling coil 22 where it is cooled to condense out any remaining entrained cresols which are collected in accumulator 23 and returned to tower 20 through conduit 24. The isobutylene vapors are carried from accumulator 23 through conduit 25, alkali scrubber 26, conduit 2'I, compressor 28, conduit 29 and condenser 30 to storage.

The extracting fluid from which the isobutylene has been released passes out of chamber l8 through conduit ll into cooling coil 42 where its temperature is reduced to a suitable temperature for introducing it into the'contact chamber [0. From the cooling coil it passes through conduit 43 into settling drum H. The cooled extracting fluid is pumped from settling drum 44 through conduit 45, pump 46 and conduit 41, and is introduced into conduit I4 through which it enters the top of contact tower l and is contacted with further quantities of C4 cut vapors.

Thus a continuous flow of extracting fluid through the system is established and a continuous supply of isobutylene is obtained.

While our invention has been described herein with reference to certain specific embodiments thereof, it is to be understood that the invention is not limited to such embodiments except as hereinafter defined in the appended claims.

What we claim is:

1. A continuous process of recovering substantially pure tertiary olefins from mixtures of light petroleum hydrocarbons comprising contacting said mixture with an extracting fluid, composed essentially of a mixture of phenols and a rela tively small amount of an acid condensing agent, at a temperature below about 80 C., separating the charged extracting fluid from the residual petroleum products, heating the charged extracting fluid to a temperature of 100 to 300 (3., collecting the tertiary olefin gas thus liberated, cooling the extracting fluid to a temperature below about 80 C. and contacting it with a further quantity of the hydrocarbon mixture.

2. A continuous process for the recovery of a substantially pure tertiary olefin from a mixture of hydrocarbons of the same number or carbon atoms comprising contacting the hydrocarbon mixture with an extracting fluid composed essentially of a mixture of phenols and a relatively small amount of an acid condensing agent at a temperature below about 80 C. separating the charged extracting fluid from the residual hydrocarbon vapors, heating the charged extracting fluid to a temperature of 100 to 300C collecting the tertiary olefin gas thus liberated, cooling the extracting fluid to a temperature below about 80 C., and contacting it with further quantities oi the hydrocarbon mixtures.

3. A continuous process for the recovery of substantially pure isobutylene from a butane cut of petroleum cracking hydrocarbons comprising contacting said butane cut with an extracting fluid composed essentially of a mixture oi phenols perature below about 80 C. and contacting it with further quantities of the butane cut.

4. A continuous process for the recovery of substantially pure trimethylethylene from a pentane cut of petroleum cracking hydrocarbons comprising contacting said pentane cut with an extracting fluid composed essentially of a mixture of phenols and a relatively small amount of an acid condensing'agent at a temperature below about 0., separating the charged extracting fluid from the residual petroleum hydrocarbons. heating the charged extracting fluid to a temperature of to 300 C., collecting the tri-- methylethylene thus liberated, cooling the extracting fluid to a temperature below about 80 C. and contacting it with further quantities of the pentane cut.

5. A continuous process for the recovery of substantially pure isobutylene from a' mixture of hydrocarbons oi the same number of carbon atoms, comprising contacting the hydrocarbon mixture with an extracting fluid composed essentiallyof a mixture of cresols and a relatively small amount of an acid condensing agent at a temperature of about 50 to 70 0., separating the charged extracting fluid from the residual hydrocarbon vapors, heating the charged extracting fluid to a temperature of about 100" to 300 C., collecting the isobutylene thus liberated,

cooling the extracting fluid to a temperature of about 50 to 70 C. and contacting it with further quantities of the hydrocarbon mixture.

6. A continuous process for the recovery of a substantially pure tertiary olefin from a mixture of hydrocarbons of the same number of carbon atoms comprising contacting the hydrocarbon mixture with an extracting fluid composed es-- sentially of a mixture of phenols and 0.01 to 3.0 per cent by weight oi an acid condensing agent at a temperature below about 80 C., separating the charged extracting fluid from the residual hydrocarbon vapors, heating the charged extracting fluid to a temperature of 100 to 300 -C., collecting the tertiary olefln gas thus liberated, cooling the extracting fluid to a temperature below about 80 C., and contacting it with further quantities oi. the hydrocarbon mixture.

7. A continuous process for the recovery of substantially pure isobutylene from a mixture of hydrocarbons of the same number 01. carbon atoms, comprising contacting the hydrocarbon mixture with an extracting fluid composed essentially of a mixture of cresols and 0.01 to 3.0 per 

